Reminds me of those stories about a US Intelligence bureau listening under the Russian embassy in Washington for keystrokes and using data analysis techniques to work out what was being typed. I think it's called "sideband data."

hehe I can just see all the paranoid folks out there screaming every time their modem lights blink...

And then there's the fone line their using, that has a scrambler and is in fact a public telephone using an acoustic coupler. In fact, they don't live in a house at all, they move from cave to cave to fool imaginary pursuers